Technical Field
The present invention relates to titanium alloys. More particularly, the present invention relates to titanium alloys that are alloyed with niobium and zirconium at specific atomic ratios by mechanical alloying and spark plasma sintering. These nanostructured titanium alloys are suited for but not limited to various biomedical and dental applications.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Titanium and titanium alloys are widely employed in biomedical and dental applications due to their excellent combination of biocompatibility, corrosion resistance and mechanical properties. Titanium and titanium alloys are characterized by their good fatigue strength, relatively low Young's or tension modulus and low densities which give high specific strength-to-weight ratios allowing lighter and stronger structures.
Titanium (Ti) alloys are generally classified into four main structural categories: alpha, near-alpha, alpha and beta, and beta. Alpha alloys contain neutral alloying elements such as tin and/or alpha stabilizers such as aluminum or oxygen only and are not heat treatable. Near-alpha Ti alloys, in addition to alpha stabilizers, are alloyed with 1-2% of beta stabilizers such as molybdenum, silicon or vanadium. Alpha and beta alloys are metastable and can be heat treated; they generally include some combination of both alpha and beta stabilizers. Beta Ti alloys are also metastable and heat-treatable, containing sufficient beta stabilizers to allow them to maintain the beta phase when quenched. Beta Ti alloys can also be solution treated and aged to improve strength.
Titanium is commonly alloyed with aluminum and vanadium to form alpha and beta Ti alloys as biomaterials, such as Ti-6Al-4V. However, Al and V pose toxicity problems and can adversely affect health. Ti-6Al-4V also suffers from poor shear strength and poor surface wer properties in certain loading conditions. More recently, beta Ti alloys with low Young's modulus and including niobium (Nb), zirconium (Zr) and tantalum (Ta) elements have been developed by melt solidification. Although Ti alloys incorporating these elements exhibit Young's modulus values that are closer to that of human bone (i.e. ˜55 GPa), Ti, Nb, Zr and Ta are difficult to melt homogeneously by a melt casting process because these elements have a large difference in melting points and specific gravities.
Additionally, nanostructured materials are known to possess unique surfaces and exceptional mechanical properties similar to those of the human bones. It has also reported that the surface of metallic materials which possess low micron to nanophase topography can enhance and increase the adhesion of osteoblasts which are cells that create the matrix of bone. Hence, nanostructured materials are considered to be the future generation orthopedic biomaterials.
It is a non-limiting objective of the present invention to provide titanium alloys that meet the criteria for biomaterials in terms of biocompatibility, resistance to corrosion, mechanical properties and cytotoxicity. It is another object to provide a bioactive surface nanomaterial that promotes a greater amount of protein adsorption to stimulate new bone formation than conventional biomaterial structure.